Objective:
Nosema disease is caused by the microsporidian parasite, Nosema ceranae, which affects bee health in many ways and is often implicated in colony declines. The only registered treatment for Nosema disease in North America is fumagillin, whose use is forbidden in Europe because it has no established Maximun Residue Level (MRL). With prolonged use of fumagillin, the issue of disease resistance to treatment arises. As a result, additional therapeutic options are urgently needed for the treatment of Nosema disease. Identifying the mechanisms that mediate host-parasite interactions and cause observed disease phenotypes can lead to the identification of specific genes and pathways that can be targeted using genomic tools, such as RNA interference (RNAi), to mitigate the impact of the parasites. With the development of high throughout transcriptome sequencing approaches expression patterns in both the host and the parasite during the course of infections can now be fully characterized. Furthermore, with the recent sequencing of the N. apis and N. ceranae genomes, it is possible to compare these two species and identify virulence factors in each species that determine pathogenesis. This information, coupled with insights into vulnerable ‘chokepoints’ in the metabolic pathways of Nosema, should lead to novel disease treatments.
This agreement supports the use of genomic and genetic techniques to improve current understanding of mechanisms of Nosema disease, leading to novel approaches, including RNAi, for enhancing honey bee immunity and suppressing parasite replication, with the following specific objectives:
Objective 1: Determine virulence factors associated with Nosema pathogenecity,
Objective 2: Identify genes that are responsible for bee defenses against Nosema infection, and
Objective 3: Develop RNAi-based therapeutics and effective delivery modes for laboratory and large-scale field application.
The long-term goal of the project is to better understand the molecular mechanisms of honey bee diseases underlying host-pathogen interactions and to bring forward the information and knowledge necessary for overcoming complex honey bee declines, including Colony Collapse Disorder (CCD). Effective and environmentally friendly technologies for control of Nosema infection and improvement of honey bee health will be developed. This research will also provide candidate genes for queen breeders for selection. It is anticipated that several RNAi targets will have the greatest impact on Nosema disease, and that these targets will form the basis of field tests aimed at providing an economical control for Nosema.

Approach:
High-throughput genome sequencing approaches will be used to explore genome-wide genetic differences between two Nosema species. RNA-Seq methods will be used to analyze transcriptome profiles indicative of host-microbe interactions. Candidate genes involved in host defense against Nosema infection will be selected for follow-up analyses using RNAi driven by presentation of double-stranded RNAs targeting specific transcripts for knockdowns. qPCR and in situ hybridization methods will be used to quantify and locate tissue-specific gene expression and to evaluate the impacts of specific RNAi constructs on bee transcripts and Nosema levels.